not sure if this is what you meant, but urinary tract infections (UTI's) and yeast infections definitely do cause buring. or if you have taken a pill called nyacin.
Things like drugs that doctors give you before major surgery to put you to sleep, you can find lists of those types of drugs on medical sites or books. Some people wood say whacking your head to...
First Google search 'spontaneous human combustion'. It is a common cause of fatalities concealed by the govt. If you recognise it early you may be able to treat. You will need to determine the source...